150 LECTURE YIU. 



Studded with cells or follicles filled with a deep brown secretion, 

 which may be regarded as hepatic follicles. The intestine is con- 

 tinued from a distinct pyloric orifice (A), which is situated at the 

 upper part of the glandular stomach near the gizzard. This orifice 

 is surrounded by vibratile cilia. The food is frequently regurgitated 

 into the gizzard, and, after having undergone additional comminution, 

 is returned to the stomach. Here it is kept in constant agitation, 

 and the particles pass by a rotatory action from the pylorus into the 

 intestine. The indigestible particles are there formed into little 

 pellets, which are carried rapidly upwards to the anal orifice (/), and 

 after being expelled, are immediately whirled away in the current 

 produced by the ciliated tentacula. The intestine in Cristatella is 

 short as compared with that in Jig. 71., and in Vesicularia. The 

 action of the sphincter may be seen when the faeces are expelled. 



A small filament, conjectured to be tubular, which passed from the 

 base of the glandular stomach to the common stem {in) supporting the 

 cell of the polype, is the only trace of the nutrient or vascular system 

 which Dr. Farre could detect. When the common stem of a ramified 

 Bryozoon is cut across, it seems to be nearly homogeneous, and does 

 not present that obvious distinction between hard and soft parts, nor 

 the canal with circulating particles, which are observed in the stems 

 of the compound Hydrozoa. Yet it can scarcely be doubted but that 

 nutrient currents must traverse the common connecting organic 

 medium or stem of the Bryozoa, both for its own support and growth, 

 and for the supply of the means of growth to the young animals ( C) 

 which are developed from it by the process of gemmation. 



The function of respiration must be referred to those parts of the 

 body which are provided with the means of efiecting a constant re- 

 newal of the surrounding oxygenized medium upon its surface. In 

 the ciliated tentacula, whose currents, Dr. Farre observes, seem much 

 beyond what is necessary to afibrd a sufiicient supply of food, we 

 most probably perceive the principal respiratory as well as prehensile 

 organs. There is a regular and uninterrupted stream of fluid in a 

 given direction in the abdominal cavity : whence it extends into the 

 canals of the tentacula. Siebold regards this movement as being 

 due to the ciliated epithelium which he detected lining the abdo- 

 minal cavity of Cristatella mirabilis and Alcyonella stagnorum. 

 Van Beneden indicates a series of pores at the bases of the tentacula 

 in the Alcyonella, which he calls " bouches aquiferes," conceiving 

 that by them water is admitted into the abdominal cavity.* 



The individuals of the Bryozoa are multiplied by two processes of 



* CXXXIV. p. 222. 



